Sea star wasting disease

Next the animal becomes limp as the water vascular system fails and it is no longer able to maintain its internal hydrostatic balance.

The body structure begins to break down, signs of stretching appear between the arms which may twist and fall off, and the animal dies.

All of these symptoms are also associated with ordinary attributes of unhealthy stars and can arise when an individual is stranded too high in the intertidal zone (for example) and simply desiccates.

[17] Scientists noticed a rapidly declining population of common starfish (Asterias rubens) occurring off the east coast of the United States.

In late August, the disease had also been found stretching from Alaska to the border of Mexico,[23] affecting more than 20 species of sea stars on the west coast of North America.

Another species also suffering mortalities was the morning sun star (Solaster dawsoni), but no cause for the deaths was apparent.

[5] The relatively high resolution of understanding of the pattern of disease spread came from marine scientists working along the coast, but also from citizen scientists visiting the coast and uploading their observations, of where they saw sea stars both with and without disease symptoms, to an online sea star wasting observation log database.

[14] At Natural Bridges State Marine Reserve in California, the ochre star is normally a common resident on the mussel beds, but by November 2013 it was reported to have completely disappeared.

[6][5][29] However, the biomass and the function of ochre sea stars in their communities, such as being important predators of mussels, has remained lower than pre-disease levels.

[5][29] Currently, most cases are located on the west coast of North America, affecting sea stars from Baja California to the gulf of Alaska.

[19] Other possible causes of the condition that have been suggested include high sea temperatures, oxygen depletion and low salinity due to freshwater runoff.

Research in 2014 showed that the cause of the disease is transmissible from one starfish to another and that the disease-causing agent is a microorganism in the virus-size range.

[36] In 2014, Point Defiance Zoo and Aquarium lost more than half of its 369 sea stars, and by September 2015 they numbered fewer than 100.

[37] The Oregon Coast Aquarium treated their affected sea stars with Seachem Reef Dip, followed by probiotics.

[38] Although a mechanism is still unknown, evidence suggests that a single mutation in the elongation factor 1-alpha locus in Pisaster ochraceus may be associated with reduced mortality.